Overview

The Airworthiness Directive (AD) AD/B747/250, amended in 2002, addresses safety concerns associated with the inadvertent deployment of thrust reversers in Boeing 747-400 series aeroplanes equipped with Pratt and Whitney PW4000 series engines. The directive was issued under the authority of the Civil Aviation Safety Authority (CASA) to enhance airworthiness standards and ensure the safety of aircraft in operation. The primary policy objective is to mitigate the risk of thrust reverser deployment during flight, which could lead to significant loss of control over the aeroplane. The AD mandates specific modifications to the aircraft's systems and components, including the installation of additional locking systems, software updates, and functional testing procedures. Compliance with these requirements is mandatory before the issuance of a Certificate of Airworthiness, ensuring that all aircraft meet stringent safety standards before being permitted to fly.

Scope and Application

The Airworthiness Directive AD/B747/250 applies specifically to Boeing Model 747-400 series aeroplanes equipped with Pratt and Whitney PW4000 series engines. The directive is issued under subregulation 39.1 (1) of the Civil Aviation Regulations 1998, and is administered by the Civil Aviation Safety Authority (CASA) delegate. The directive outlines requirements necessary to correct an unsafe condition related to the inadvertent deployment of the thrust reverser during flight, which can lead to reduced controllability of the aeroplane. The directive mandates the installation of additional locking systems on each engine thrust reverser and modifications to the central maintenance computer system hardware and software, as well as the integrated display system software. It also requires specific functional tests to detect discrepancies and correct any identified issues. Compliance with these requirements must be achieved before issuing a Certificate of Airworthiness for certain modifications and before further flight for others. Additionally, certain repetitive functional tests must be carried out at intervals not exceeding 4000 hours of time-in-service. The directive became effective on 5 September 2002, as published in the Commonwealth of Australia Gazette on 14 August 2002.

Key Provisions

The Airworthiness Directive (AD) AD/B747/250 Amdt 1, issued under subregulation 39.1 (1) of the Civil Aviation Regulations 1998, applies specifically to Boeing 747-400 series aeroplanes equipped with Pratt and Whitney PW4000 series engines. This directive aims to address safety concerns regarding the inadvertent deployment of thrust reversers during flight, which could reduce the controllability of the aeroplane. The AD mandates specific actions to be taken to ensure the safety of the aircraft. The requirements outlined in the directive are multifaceted. Firstly, it mandates the installation of an additional locking system on each engine thrust reverser, as detailed in Boeing Service Bulletin (SB) 747-78-2155, Revision 2, dated 5 November 1998. Secondly, it requires modifications to the central maintenance computer system hardware and software, in line with Boeing SB 747-45-2016, Revision 1, dated 2 May 1996. Additionally, the integrated display system software must be modified in accordance with Boeing SB 747-31-2245, dated 27 June 1996. A provisional wiring installation for the locking system must also be completed, following Boeing SB 747-78-2154, Revision 3, dated 11 December 1997. Following these modifications, a function test must be performed to detect any discrepancies with the newly installed locking system, as detailed in Appendix 1 of FAA AD 2000-12-21 Amendment 39-11799. Any detected discrepancies must be corrected in line with approved maintenance data, followed by another function test to ensure the system operates correctly. The AD imposes several obligations on the entities it governs. These entities are required to implement the specified modifications and tests in a timely manner, ensuring that the aircraft meet the safety standards set forth by the Civil Aviation Safety Authority (CASA). Specifically, certain modifications must be completed prior to the issuance of a Certificate of Airworthiness. Other tasks, such as the function tests and corrections of any detected discrepancies, must be completed before further flight operations can occur. These obligations ensure that the safety measures are implemented effectively and that the aircraft remain airworthy. Failure to comply with the requirements of this Airworthiness Directive can result in serious consequences. While specific penalties are not detailed in the text, non-compliance with CASA directives can typically result in civil penalties, including fines, or in more severe cases, criminal charges. The safety and airworthiness of the aircraft are paramount, and any breach of the AD could potentially lead to accidents or incidents that endanger lives. Therefore, it is crucial for the governed entities to adhere strictly to the mandated requirements to avoid any legal or safety repercussions.